When the action movie Cloverfield thrilled audiences in 2008, few in theaters could have guessed that it was, at least in part, under the creative stewardship of Steven Spielberg.

That’s because Spielberg has no credit on the production.

That didn’t stop him from giving the movie’s director, Matt Reeves, and its producer, J.J. Abrams, advice on how to improve the film.

“He had this idea about the ending,” said Reeves, who, with Abrams, had sent Spielberg a cut during post-

production with the hope that he would give them creative notes.

The early version showed the giant monster that wreaks havoc on New York being last seen on the loose, at war with fighter jets.

“The movie was meant to be open-ended, but something was missing,” Reeves said.

Spielberg suggested the inclusion of air-raid sirens to give the impression of a countdown.

“It prepared you so that even though the ending was still inconclusive, it wasn’t letting you fall off a cliff,” Reeves said. “It helped the movie a lot.”

Spielberg, 66, is considered the most influential director of our time, thanks to the strength of the more than two dozen features he has

directed. In addition, he has in one form or another been ultimately responsible for more than 175 films — mostly through his production company, Amblin, and his studio, DreamWorks.

Less visible, though, is the feedback that Spielberg has provided as a sounding board for filmmakers not necessarily under his authority. Being the recipient of such creative input is as close to receiving a benediction as one can hope for in Hollywood.

“His love of movies and desire to collaborate extends far beyond those projects that he is required to work on,” Abrams said. “But he is so frequently cornered by people and asked to give notes. I feel guilty about being one of them.”

For Trek, which he saw in an early cut, Spielberg suggested lengthening several scenes and advised that the female communications officer, Uhura, be developed further.

“I think, for Steven, sometimes it’s the most fun to weigh in on someone else’s work when there are no consequences,” said David Koepp, who has worked as a writer and director on several Spielberg productions. “He is free to just talk about the creative part.”

Koepp asked Spielberg to read an early draft of the script for Premium Rush (2012), which Koepp directed but to which Spielberg had no affiliation. The film features a bike messenger engaged in several chase sequences from one tip of Manhattan to another and back again.

Spielberg’s advice to Koepp was to show the main character entering the screen consistently from one side when he was going downtown, and to enter the other side when he was going uptown, to help orient the audience.

“He is exceedingly practical and grounded in the storytelling,” Koepp said. In giving his notes, Spielberg referred to how Peter O’Toole’s character in Lawrence of Arabia does the same thing when his character crosses the desert.

Premium Rush benefited from that “simple geographical clue,” said Koepp, who added that while it is not uncommon for well-acquainted filmmakers to ask one another to give notes, Spielberg’s come with a signature “undercurrent of kindness.”

“The times when I have seen him the most happy are when he has been in the process of making stuff up,” he said. “There is so much that can slow you down when you are making a movie.”

Abrams said Spielberg’s enthusiastic notes don’t infringe on the autonomy of directors who work under him. “He doesn’t mandate,” said Abrams, who directed Super 8 (2011), which Spielberg produced.

When Chris Columbus wrote Gremlins (1984), which he directed, it was originally a horror film with a “hard R” rating, he said, about critters that tear up a town. But Spielberg, his executive producer, suggested not letting all of the gremlins turn malicious, and keeping one of them, Gizmo, good. It was a change that “taught me how the audience could become emotionally attached to the film,” Columbus said.

Spielberg’s advice ranges from what sounds apocryphal (telling Sam Mendes, the first-time director of American Beauty to wear comfortable shoes on the set of the 1999 film) to the technical (advising Robert Zemeckis to use wide camera lenses on his 1978 directorial debut, I Wanna Hold Your Hand.)

“He is so aware of the geography of storytelling,” said Abrams, who said he plans to show Spielberg a cut of Star Trek Into Darkness, due in May, within the next few weeks.

A spokesman for Spielberg said he “considers his conversations with other filmmakers to be private,” so he did not comment for this story.